MADRID, Spain — The suspected leader of a militant Muslim cell plotted to deal Spain the “biggest blow of its history” — a suicide truck bomb laden with half a ton of explosives aimed at killing the country’s top judges investigating Islamic terror and destroying their case files, officials said Wednesday.

Police said they had intercepted hundreds of letters from suspected cell members in which they said they were willing to stage suicide attacks.

The plot to blow up the National Court, Spain’s nerve center for investigating Islamic terror, was detailed in a report from the National Police intelligence unit obtained by the Associated Press. The report quotes a protected witness who had been in contact with the suspected ringleader Mohamed Achraf, an Algerian born in the United Arab Emirates.

Spain said Achraf was recently arrested in Switzerland. Switzerland confirmed Wednesday he is in custody there for entering the country illegally and said deportation proceedings were pending when his alleged link to the plot surfaced.

Anti-terror judge to seek extradition
Spain’s leading anti-terrorism magistrate, Judge Baltasar Garzon, is preparing to send the Swiss authorities a warrant spelling out specific charges against Achraf, setting the stage for Spain’s government to request his extradition, sources at Spain’s National Court said.

Achraf is the suspected leader of a Muslim terrorist cell that plotted to detonate a truck packed with 1,100 pounds of compressed dynamite outside the National Court, located on a bustling avenue in downtown Madrid, according to the report.

He had served time for credit card fraud in a jail near Salamanca in western Spain where he sought recruits among prisoners. He was in Spain when he plotted the attack, police said.

Eight suspected members of Achraf’s cell were arrested in Spain on Monday and Tuesday.

The Interior Ministry said wiretapped phone conversations showed the cell had been talking about bombing the National Court, but no explosives were found in the raids.

“If Spain loses three or four of its most important judges, that is worse than losing its prime minister,” the report said, quoting testimony the informant gave on his conversations with Achraf.

‘The biggest blow’“Achraf told the witness, in a closed meeting, that he needed to give Spain the biggest blow of its history, for which he needed 1,000 kilograms (2,200 pounds) of Goma 2,” the report read. Goma 2 is a kind of compressed dynamite.

The witness told police Achraf was considering using a truck bomb loaded with 1,100 pounds of the explosives for a first attack, targeting the National Court. The report made no mention of what he planned to do with the rest of the explosives.

“He wanted the attack to be at the National Court in Madrid or the Supreme Court,” the report said.

“Furthermore with this attack, many case files related to mujahedeen would be destroyed,” the witness said, according to the police report.

Garzon, an investigative judge at the National Court specializing in anti-terrorism, has over the past year indicted 41 people on terrorism charges, including Osama bin Laden and other al-Qaida suspects accused of staging the Sept. 11 attacks on New York and Washington. That case file alone is believed to be tens of thousands of pages long.

Another judge at the court, Juan del Olmo, is leading the probe into the March 11 train bombings in Madrid, which killed 191 people and have been blamed on Muslim militants linked to al-Qaida.

Plot allegedly hatched in jailAchraf said many Muslims in Spanish jails wanted to get out “and have the opportunity to die as martyrs. In any case, Achraf made clear that the day of the attack, he would be the first martyr,” the informant is quoted as saying.

The protected witness gave this testimony on Sept. 14, triggering a police operation that led to the eight arrests this week.

Video: Madrid bombing video released
The ministry said the suspects had contacts elsewhere in Europe, the United States and Australia. Australian police said Wednesday they were investigating a suspect whose name was passed on to them by Spain. In the report’s only mention of the Madrid train bombings, the informant quoted Achraf as saying increased airline security after Sept. 11, 2001, had made the March 11 attack possible.

“After Sept. 11, all eyes turned to the skies, monitoring flights, and this helped stage the March 11 attacks on the trains,” the report said.

The witness quoted in the report is not named, only identified by a number. The only detail on him in the report says that he knew many Muslims through a mosque in the southern town of Roquetas de Mar.

Word of the plot came a day after chilling security-camera videotape of the March 11 train bombings was broadcast by a Spanish TV station.

The video, taken at Madrid’s Atocha station and aired by Telecinco, is believed to be the first public broadcast of images from the bombings that killed 191 people.

The video of the March 11 attacks begins after one bomb has already exploded, with dazed commuters milling about on a smoke-shrouded platform. The time on the tape says 7:38 a.m.

Then, smoke flows toward the camera and people on the platform are knocked over — apparently by another blast.

Rush-hour horror
About five seconds later, a ball of orange flames erupts from a stopped train, filling the screen. The tape includes no sound, just images.

The video appeared to have been taken from atop an escalator, looking down onto the platform.

Four minutes later, bodies are seen strewn on the platform amid puddles of blood. Police and emergency medical staffers attend to them.

After another five minutes, police and crews are seen screaming for people to evacuate the station and themselves are seen running toward the escalator in fear of another explosion. Telecinco said this warning turned out to be a false alarm.

Telecinco also broadcast two other pieces of March 11 video that had not been broadcast publicly, although their existence was known.

One shows a gun-carrying, masked militant claiming responsibility for the attacks on behalf of al-Qaida. The video was found near a mosque on the eve of Spain’s March 14 general election.

In the other video, made March 27, three hooded men wearing belts loaded with dynamite cartridges threaten more attacks against Spain unless it withdraws its troops from Afghanistan.